17th Amendment to the U.S. Constitution: Direct Election of U.S. Senators. Americans did not directly vote for senators for the first 125 years of the Federal Government. The Constitution, as it was adopted in 1788, stated that senators would be elected by state legislatures.
The high growth of population in Terai region is because of migration from mountain and hill , growth of the population in the Terai region itself and immigration from outside i.e. from other neighbouring countries